title: Integral role of platelet-derived growth factor in mediating transforming growth factor-β1-dependent mesenchymal stem cell stiffening.
abstract: Mesenchymal stem cells (MSCs) play an important role in matrix remodeling, fibroblast activation, angiogenesis, and immunomodulation and are an integral part of fibrovascular networks that form in developing tissues and tumors. The engraftment and function of MSCs in tissue niches is regulated by a multitude of soluble proteins. Transforming growth factor-β1 (TGF-β1) and platelet-derived growth factor-BB (PDGF) have previously been recognized for their role in MSC biology; thus, we sought to investigate their function in mediating MSC mechanics and matrix interactions. Cytoskeletal organization, characterized by cell elongation, stress fiber formation, and condensation of actin and microtubules, was dramatically affected by TGF-β1, individually and in combination with PDGF. The intracellular mechanical response to these stimuli was measured with particle tracking microrheology. MSCs stiffened in response to TGF-β1 (their elastic moduli was ninefold higher than control cells), a result that was enhanced by the addition of PDGF (100-fold change). Blocking TGF-β1 or PDGF signaling with inhibitors SB-505124 or JNJ-10198409, respectively, reversed soluble-factor-induced stiffening, indicating that crosstalk between these two pathways is essential for stiffening response. A genome-wide microarray analysis revealed TGF-β1-dependent regulation of cytoskeletal actin-binding protein genes. Actin crosslinking and bundling protein genes, which regulate cytosolic rheology through changes in semiflexible actin polymer meshwork, were upregulated with TGF-β1 treatment. TGF-β1 alone and in combination with PDGF also amplified surface integrin expression and adhesivity of MSCs with extracellular matrix proteins. These findings will provide a more mechanistic insight for modeling tissue-level rigidity in fibrotic tissues and tumors.
authors.affiliation: 1 Georgia Institute of Technology , School of Chemical and Biomolecular Engineering, Atlanta, Georgia .
authors.forename: Deepraj
authors.initials: D
authors.lastname: Ghosh
authors.forename: Loukia
authors.initials: L
authors.lastname: Lili
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: McGrail
authors.forename: Lilya V
authors.initials: LV
authors.lastname: Matyunina
authors.forename: John F
authors.initials: JF
authors.lastname: McDonald
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Dawson
mesh_terms: D000818:Animals; D052117:Benzodioxoles / Q000494:pharmacology; D001696:Biomechanical Phenomena; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004357:Drug Synergism; D055119:Elastic Modulus; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D007093:Imidazoles / Q000494:pharmacology; D007189:Indans / Q000494:pharmacology; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D061251:Primary Cell Culture; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D053773:Transforming Growth Factor beta1 / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: C505208:(6,7-dimethoxy-2,4-dihydroindeno(1,2-c)pyrazol-3-yl)(3-fluorophenyl)amine; C519132:2-(5-benzo(1,3)dioxol-5-yl-2-tert-butyl-3H-imidazol-4-yl)-6-methylpyridine hydrochloride; D052117:Benzodioxoles; D007093:Imidazoles; D007189:Indans; D008840:Microfilament Proteins; D010982:Platelet-Derived Growth Factor; D011720:Pyrazoles; D011725:Pyridines; D053773:Transforming Growth Factor beta1